ISTANBUL, May 13 (Reuters) - A fire in a coal mine in Turkey's western province of Manisa killed 20 miners on Tuesday, a local lawmaker said, and rescue workers said as many as 300 more may still be trapped.

Local member of parliament Muzaffer Yurttas told broadcaster NTV that the bodies of 20 workers, believed to have died from suffocation and burns, had been retrieved from the mine and that at least another 20 workers had been taken to hospital.

"They are pumping oxygen into the mine, but the fire is still burning. They say it is an electrical fault but it could be that coal is burning as well," Tamer Kucukgencay, chairman of the regional labour union, told Reuters by telephone.

Energy Minister Taner Yildiz confirmed that a fire had been triggered by an electrical fault and that workers had been killed, but declined to say how many.

The blast happened during a change in shifts, leading to uncertainty over the exact number of workers still in the mine, labour union officials said.

Nurettin Akcul, national head of the Turkish Mineworkers' Union (Maden-Is), told CNN Turk television that an unknown number were still trapped after the blast, which he said happened around 2 km (miles) below ground.

Mehmet Bahattin Atci, mayor of Soma, a district in Manisa, said 200-300 workers were still inside following the explosion. The head of the local fire service also told Turkish television that around 300 workers were still trapped.